Paper sheet multi-feed preventing member

ABSTRACT

A paper sheet multi-feed preventing member  3  being planar includes an outer layer  8  which comes into contact with a paper sheet  5  and an inner layer  9  laminated on the outer layer  8,  the inner layer  9  has a type A durometer hardness not less than A5/S and not more than A60/S, or an Asker-C hardness not less than C5 and not more than C50, and the outer layer  8  has a rubber hardness higher than that of the inner layer  9.

BACKGROUND OF THE INVENTION

The present invention relates to a paper sheet multi-feed preventing member having a planar shape, which is installed and used in a paper feed mechanism, etc., of a laser beam printer, etc., for separating a plurality of stacked paper sheets and supplying them to the laser beam printer, etc., one by one.

For example, in a paper cassette or a paper feed tray, etc., of a laser beam printer (hereinafter, abbreviated to “LBP” in some cases), a paper feed mechanism for preventing erroneous feeding (multi-feed) of two or more paper sheets, stacked and accommodated in the paper cassette or paper feed tray, etc., while overlapping each other is provided. The paper feed mechanism usually includes a paper feed roller at least the outer peripheral surface of which is made of an elastomer such as rubber, and a paper sheet multi-feed preventing member in contact with the outer peripheral surface of the paper feed roller.

The paper feed mechanism operates to supply only a first paper sheet in contact with the paper feed roller to an LBP, etc., by separating it from other paper sheets by rotation of the paper feed roller while restraining conveyance of second and subsequent paper sheets by frictional force of the paper sheet multi-feed preventing member.

As the paper sheet multi-feed preventing member, there is a so-called separation pad being planar and entirely integrally made of an elastomer such as rubber, a separation roller at least the outer peripheral surface of which is made of an elastomer such as rubber, and so on.

The separation roller of these is superior in terms of the function of separating (separating function) two or more overlapping paper sheets by restraining conveyance of second and subsequent paper sheets by frictional force, and can reliably separate various sheets (plain paper, coated paper, and cardboard, etc.) as paper sheets and plastic films, etc.

Therefore, in many full color-capable LBPs frequently used for image forming onto various paper sheets (hereinafter, abbreviated to “color LBPs” in some cases), etc., a separation roller is adopted as a paper sheet multi-feed preventing member (refer to Patent documents 1 and 2, etc.).

On the other hand, in many monochrome-type LBPs (hereinafter, abbreviated to “monochrome LBPs” in some cases), etc., for which the kinds of paper sheets to be used are few and which are required to have an entire structure as simple as possible, a separation pad having a smaller number of components and a simpler structure than those of the separation roller is used as the paper sheet multi-feed preventing member (refer to Patent documents 3 to 5).

[Prior Art Documents][Patent document 1] Japanese Published Unexamined Patent Application No. 2007-137539

[Patent document 2] Japanese Published Unexamined Patent Application No. 2008-114935

[Patent document 3] Japanese Published Unexamined Patent Application H05-43070

[Patent document 4] Japanese Patent Publication No. 3977819

[Patent document 5] Japanese Patent Publication No. 4176592

Recently, simplification of the entire structure of color LBPs has been demanded for further widespread use of color LBPs, and as part of this, use of a separation pad instead of the separation roller is also considered for color LBPs.

However, a conventional separation pad which is entirely made of an elastomer such as rubber integrally is small in contact length (nipping width) in the paper sheet feed direction with the paper feed roller, and easily slips from a paper sheet, so that the separating function described above cannot be sufficiently obtained. Particularly, the kinds of paper sheets which the separation pad can separate are limited, and various kinds of paper sheets cannot be reliably separated.

Further, the conventional separation pad is easily worn away, and the thickness is reduced in a short time due to this wear, and further, the separating function is deteriorated. One of the causes of easy wear of the separation pad is frequent friction with paper sheets caused by slipping.

The conventional separation pad has a small nipping width as described above, and a contact force caused by contact with the paper feed roller is easily concentrated at a comparatively narrow area, so that the load to be applied to the separation pad by the contact is great, and this is one of the causes of easy wear.

Further, the conventional separation pad easily causes chatter vibration due to friction with a paper sheet or a phenomenon called screeching that is an abnormal sound in conjunction with the friction. The cause of these is also the small nipping width which causes a contact force of contact with the paper feed roller to easily concentrate at a narrow area and increases the load to be applied to the separation pad due to the contact.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a separation pad, that is, a paper sheet multi-feed preventing member which has a planar shape and has an excellent separating function, and accordingly, can adapt to various kinds of paper sheets, and does not easily wear away, and hardly causes chatter vibration and screeching, etc., without greatly complicating the structure as compared with the conventional separation pad.

The inventor considered various solutions to the problem, and found a solution in which the paper sheet multi-feed preventing member having a planar shape was formed to have a laminate structure including an outer layer which came into contact with a paper sheet and an inner layer which was laminated on the outer layer, and the rubber hardness of the outer layer of these layers was set equivalent to the conventional structure and the rubber hardness of the inner layer was set in a predetermined range lower than the outer layer.

That is, the present invention provides a paper sheet multi-feed preventing member being planar and including an outer layer which comes into contact with the paper sheet and an inner layer laminated on the outer layer, the inner layer has a type A durometer hardness not less than A5/S and not more than A60/S, and the outer layer has a rubber hardness higher than that of the inner layer.

Further, the present invention provides a sheet multi-feed preventing member being planar and including an outer layer which comes into contact with the paper sheet and an inner layer laminated on the outer layer, and the inner layer has an Asker (registered trademark)-C type hardness not less than C5 and not more than C50, and the outer layer has a rubber hardness higher than that of the inner layer.

As described above, by forming the paper sheet multi-feed preventing member so as to have a laminate structure and setting the rubber hardness of the inner layer in the predetermined range lower than the rubber hardness of the outer layer corresponding to the conventional separation pad, when it is brought into contact with the outer peripheral surface of the paper feed roller, the paper sheet multi-feed preventing member can be compressed and deformed in the thickness direction greater than the conventional single-layer structure.

Therefore, the contact length (nipping width) in the paper sheet feed direction with the paper feed roller can be increased and slipping from the paper sheets can be made hard to occur, and the separating function of separating two or more overlapping paper sheets by restraining conveyance of second and subsequent paper sheets by frictional force of the paper sheet multi-feed preventing member can be made more excellent than conventionally.

Further, by suppressing friction with the paper sheets caused by slipping and making the inner layer softer, the contact force of the paper feed roller is reduced on the surface of the paper sheet multi-feed preventing member, and the load to be applied to the paper sheet multi-feed preventing member due to the contact with the paper feed roller is eased, and by the synergistic effects of these, rapid wear of the outer layer can be suppressed. Therefore, the problem in which the thickness of the paper sheet multi-feed preventing member is greatly reduced in a comparatively short time due to the wear and the separating function is deteriorated can be made hard to occur.

Further, as described above, the load to be applied to the paper sheet multi-feed preventing member due to contact with the paper feed roller can be reduced, so that chatter vibration and screeching, etc., due to friction with the paper sheet can also be suppressed.

The outer layer and the inner layer of the paper sheet multi-feed preventing member of the present invention can be both made of various elastomers having rubber elasticity, and particularly preferably, the inner layer having a type A durometer hardness not less than A5/S and not more than A60/S is made of non-porous material of butyl rubber.

By making the inner layer of a non-porous material of butyl rubber having the above-described rubber hardness and excellent vibrational absorbability, chatter vibration and screeching, etc., due to friction with a paper sheet, etc., can be more reliably suppressed.

It is preferable that the thickness of the outer layer is not less than 0.1 millimeters and not more than 2.0 millimeters, and the thickness of the inner layer is not less than 0.5 millimeters and not more than 5.0 millimeters. By setting the thicknesses of both layers within these ranges, the various effects described above can be further improved.

The inner layer having an Asker-C hardness not less than C5 and not more than C50 is preferably made of a porous material of butyl rubber.

By making the inner layer of a porous material of butyl rubber having the rubber hardness and vibrational absorbability, chatter vibration and screeching, etc., due to friction with the paper sheet, etc., can be more reliably suppressed.

It is preferable that the thickness of the outer layer is not less than 0.1 millimeters and not more than 2.0 millimeters, and the thickness of the inner layer is not less than 0.5 millimeters and not more than 5.0 millimeters. By setting the thicknesses of both layers within these ranges, the various effects described above can be further improved.

The present invention can provide a paper sheet multi-feed preventing member which has a planar shape and has an excellent separating function, and accordingly, can adapt to various kinds of paper sheets, and does not easily wear away, and hardly causes chatter vibration and screeching, etc., without greatly complicating the structure as compared with the conventional separation pad.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an example of a preferred embodiment of a paper sheet multi-feed preventing member of the present invention.

FIG. 2 is a schematic sectional view showing an example of a paper feed mechanism in which the paper sheet multi-feed preventing member of the example of FIG. 1 is installed.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective view showing an example of a preferred embodiment of a paper sheet multi-feed preventing member of the present invention. FIG. 2 is a schematic sectional view showing an example of a paper feed mechanism in which the paper sheet multi-feed preventing member of the example is installed.

Referring to FIG. 2, the paper feed mechanism 1 of this example includes a paper feed roller 2 made of an elastomer such as rubber, and a paper sheet multi-feed preventing member (separation pad) 3 in contact with the outer peripheral surface of the paper feed roller 2.

The paper sheet multi-feed preventing member 3 has a planar shape, and is held by a support base 6 in a state in which the surface 4 (upper surface in the figure) thereof is exposed and other surfaces are protected by the support base 6.

The paper sheet multi-feed preventing member 3 has the surface 4 brought into contact with the outer peripheral surface 7 of the paper feed roller 2 by a predetermined contact force by pressing the support base 6 in the direction toward the outer peripheral surface 7 as shown by the outline arrow in the figure by a spring member, etc., not shown in a state in which the surface 4 is opposed to the outer peripheral surface 7 of the paper feed roller 2.

The paper feed mechanism 1 operates to separate only the first paper sheet 5 in contact with the paper feed roller from other paper sheets 5 by rotation in the direction of the arrow indicated by the long and short dashed line in the figure of the paper feed roller while restraining conveyance of second and subsequent paper sheets 5 of the paper sheets 5 stacked and accommodated in a paper cassette or a paper feed tray due to friction of the paper sheet multi-feed preventing member 3, and supplies it to the LBP, etc., as shown by the solid-line arrow in the figure.

Referring to FIG. 1, the paper sheet multi-feed preventing member 3 of this example includes an outer layer 8 having a rectangular planar shape and an upper surface formed as the surface 4 which comes into contact with a paper sheet, and an inner layer 9 which has a rectangular planar shape and is laminated on the outer layer 8.

The layers 8 and 9 are made of an elastomer with rubber elasticity, and the inner layer 9 of these layers must have:

-   -   (1) a type A durometer hardness not less than A5/S and not more         than A60/S at a temperature of 23±1° C. and a relative humidity         of 55±1%, measured according to the measuring method regulated         in “Rubber, vulcanized or thermoplastic—Determination of         hardness” of JIS K 6253 2006, or     -   (2) an Asker-C hardness not less than C5 and not more than C50         at a temperature of 23±1° C. and a relative humidity of 55±1%,         measured according to the measuring method regulated in         “Physical Testing Method for Expanded Rubber,” The Society of         Rubber Ind., Japanese Standard 0101.

(1) described above shows the range regulating the rubber hardness of the inner layer 9 when the inner layer 9 is mainly made of a non-porous material of an elastomer such as rubber. The reason for the limitation of the type A durometer hardness of the inner layer 9 made of the non-porous material to the range is as follows.

That is, it is substantially difficult to make a non-porous material as soft as a type A durometer hardness less than A5/S of a conventionally known elastomer. Even if this is possible, the non-porous material is so soft that formation of the paper sheet multi-feed preventing member 3 by using the non-porous material as the inner layer 9 and laminating it on the outer layer 8 is substantially difficult.

Therefore, the type A durometer hardness of the inner layer 9 made of the non-porous material must be not less than A5/S.

On the other hand, if the type A durometer hardness of the inner layer 9 is more than A60/S, the effect realized by providing the paper sheet multi-feed preventing member 3 with a laminate structure including the inner layer 9 and the outer layer 8 and softening the inner layer 9 cannot be obtained.

That is, when the paper sheet multi-feed preventing member 3 is brought into contact with the outer peripheral surface 7 of the paper feed roller, the paper sheet multi-feed preventing member 3 cannot be compressed and deformed in the thickness direction greater than the conventional single-layer structure. Therefore, the effects which improve the separating function and make the paper sheet multi-feed preventing member 3 adaptable to various kinds of paper sheets, make the paper sheet multi-feed preventing member difficult to wear, and make chatter vibration and screeching, etc., hard to occur, cannot be obtained.

Therefore, the type A durometer hardness of the inner layer 9 made of a non-porous material must be not more than A60/S.

For further improving the effect obtained by making the inner layer 9 as soft as possible and forming the laminate structure of the paper sheet multi-feed preventing member 3 while securing excellent machinability when forming the non-porous material of the inner layer 9 and laminating the formed inner layer 9 on the outer layer 8, the type A durometer hardness of the inner layer 9 is preferably not less than A5/S and not more than A40/S, and especially preferably not less than A5/S and not more than A30/S within the range.

The inner layer 9 of the non-porous material with a type A durometer hardness within the range can be made of one or two or more kinds of conventionally known various elastomers such as acrylonitril-butadiene rubber (NBR), butyl rubber, styrene-butadiene rubber (SBR), natural rubber (NR), urethane rubber, and styrenic thermoplastic elastomers.

Particularly preferably, the inner layer 9 is made of a non-porous material of butyl rubber. Butyl rubber has vibrational absorbability especially excellent in an ordinary temperature range (5 to 35° C.), so that chatter vibration and screeching, etc., caused by friction with paper sheets can be more reliably suppressed.

The non-porous inner layer 9 can be formed by, for example, kneading an elastomer as a raw material with various additives as appropriate and then molding the material into a sheet shape, and further vulcanizing it when the elastomer is vulcanized rubber.

For adjusting the type A durometer hardness of the inner layer 9 made of the non-porous material to a value within the range described above, when the elastomer is vulcanized (crosslinkable) rubber, the kind, the molecular weight (average molecular weight, molecular weight distribution, etc.), the molecular structure (linear or branched, etc.), or the degree of cure (degree of crosslinking) of the rubber is adjusted. Alternatively, the amounts of oil, plasticizer, and stiffener, etc., may be adjusted. For adjusting the degree of cure of the rubber, the kinds and blending amounts of additives such as the vulcanizing agent, the cross-linking agent, the vulcanization accelerator, are adjusted.

(2) described above shows the range regulating the rubber hardness of the inner layer 9 when the inner layer 9 is mainly made of a porous material of an elastomer such as rubber. The reason for limitation of the Asker-C hardness of the inner layer 9 made of the porous material to not less than C5, not more than C50 is as follows.

That is, it is substantially difficult to make a porous material as soft as an Asker-C hardness less than C5 of a conventionally-known elastomer. Even if this is possible, such a porous material is so soft that it is substantially difficult to form the paper sheet multi-feed preventing member 3 by using the porous material as the inner layer 9 and laminating it on the outer layer 8.

Therefore, the Asker-C hardness of the inner layer 9 made of a porous material must be not less than C5.

On the other hand, if the Asker-C hardness of the inner layer 9 is more than C50, the effect realized by providing the paper sheet multi-feed preventing member 3 with a laminate structure including the inner layer 9 and the outer layer 8 and softening the inner layer 9 cannot be obtained.

That is, when the paper sheet multi-feed preventing member 3 is brought into contact with the outer peripheral surface 7 of the paper feed roller, the paper sheet multi-feed preventing member 3 cannot be compressed and deformed in the thickness direction greater than the conventional single-layer structure. Therefore, the effects which improve the separating function and make the paper sheet multi-feed preventing member 3 adaptable to various kinds of paper sheets, make the paper sheet multi-feed preventing member difficult to wear, and make chatter vibration and screeching, etc., hard to occur, cannot be obtained.

Therefore, the Asker-C hardness of the inner layer 9 made of the porous material must be not more than C50.

For further improving the effect obtained by making the inner layer 9 as soft as possible and forming the laminate structure of the paper sheet multi-feed preventing member 3 while securing excellent machinability when forming the porous material of the inner layer 9 and laminating the formed inner layer 9 on the outer layer 8, the Asker-C hardness of the inner layer 9 is preferably not less than C10 and not more than C45, and especially preferably not less than C10 and not more than C30 within the range.

The porous inner layer 9 with an Asker-C hardness within the range can be made of one or two or more kinds of various conventionally-known elastomers such as NBR, butyl rubber, SBR, NR, urethane rubber, and styrenic thermoplastic elastomers.

Especially preferably, the inner layer 9 is made of a porous material of butyl rubber. Butyl rubber has excellent vibration absorbability especially in an ordinary temperature range (5 to 35° C.), so that chatter vibration and screeching, etc., due to friction with the paper sheet can be more reliably suppressed.

The inner layer 9 made of the porous material can be formed according to various conventionally-known methods. For example, at an arbitrary time during the formation of the inner layer 9 by kneading an elastomer as a raw material with various additives as appropriate and then molding the material, and further vulcanizing it when the elastomer is vulcanized rubber, that is, for example, at the same time as the vulcanization when the elastomer is vulcanized rubber, by foaming a foaming agent added in advance to the elastomer, the inner layer 9 made of the porous material can be formed. The inner layer 9 made of the porous material can also be formed by eluting water-soluble particles of salt, etc., added in advance to the elastomer at an arbitrary time after molding, that is, for example, after vulcanization when the elastomer is vulcanized rubber.

For adjusting the Asker-C hardness of the inner layer 9 made of the porous material to a value within the range, the porous structure of the porous material (whether the porous material has a continuous porous structure or an independent porous structure, etc.) is selected or the porosity is adjusted. For example, when the elastomer is vulcanized (crosslinkable) rubber, the kind and the molecular weight (average molecular weight, molecular weight distribution, etc.), the molecular structure (linear or branched, etc.), or the degree of cure (degree of crosslinking) of the rubber is adjusted. Alternatively, the amounts of oil, plasticizer, and stiffener, etc., may be adjusted. For adjusting the degree of cure of the rubber, the kinds and blending amounts of additives such as the vulcanizing agent, the cross-linking agent, the vulcanization accelerator, are adjusted.

As the outer layer 8 which is laminated on the inner layer 9 satisfying either (1) or (2) and constitutes the surface 4 of the paper sheet multi-feed preventing member 3, various layers with rubber hardness higher than that of the inner layer 9 satisfying either (1) or (2) are usable. However, the type A durometer hardness of the outer layer 8 is preferably not less than A60/S and not more than A95/S, and especially preferably not less than A75/S and not more than S90/S.

If the type A durometer hardness of the outer layer 8 is less than A60/S, there is a possibility that the surface 4 of the paper sheet multi-feed preventing member 3 as the surface of the outer layer 8 becomes so soft that it may be worn away due to friction with the paper sheet. Therefore, this wear may greatly reduce the thickness of the paper sheet multi-feed preventing member 3 in a comparatively short time and deteriorate the separating function.

On the other hand, if the type A durometer hardness of the outer layer 8 is more than A95/S, there is a possibility that the outer layer 8 becomes so hard that the paper sheet multi-feed preventing member 3 cannot be greatly compressed and deformed in the thickness direction when the paper sheet multi-feed preventing member 3 is brought into contact with the outer peripheral surface 7 of the paper feed roller. Therefore, there is a possibility that the effects which improve the separating function and make the paper sheet multi-feed preventing member 3 adaptable to various kinds of paper sheets, make the paper sheet multi-feed preventing member difficult to wear, and make chatter vibration and screeching, etc., hard to occur, cannot be obtained.

The outer layer 8 is preferably made of a non-porous material. If a porous material is used, there is a possibility that an outer layer 8 with rubber hardness higher than that of the inner layer 9, specifically, an outer layer 8 with a type A durometer hardness within the range, cannot be formed. The outer layer 8 made of a porous material is easily worn by friction with the paper sheet even if the type A durometer hardness is within the range, so that the wear may greatly reduce thickness of the paper sheet multi-feed preventing member 3 in a comparatively short time and easily deteriorate the separating function.

The outer layer 8 can be made of one or two or more kinds of variously conventionally-known elastomers such as polyester-based thermoplastic elastomers, styrenic thermoplastic elastomers, ethylene-propylene-diene rubber (EPDM), urethane rubber, NBR, and urethane-based thermoplastic elastomers (TPU).

As polyester-based thermoplastic elastomers, one or two or more kinds of various thermoplastic polyester elastomers consisting of multi-block polymers including high-melting point and high-crystalline aromatic polyester (polybutylene terephthalate, etc.) as a hard segment and amorphous polyether (polytetramethylene ether glycol) whose glass transition temperature is not more than −70° C. as a soft segment are usable.

The outer layer 8 made of a non-porous material can be formed by, for example, kneading an elastomer as a raw material with various additives as appropriate and then molding the material into a sheet shape, and further vulcanizing it when the elastomer is vulcanized rubber.

For adjusting the type A durometer hardness of the outer layer 8 to a value within the range, for example, in the case of a polyester-based thermoplastic elastomer, the kinds and lengths of blocks forming the hard segment and the soft segment or the ratio of these segments, etc., are adjusted.

In the case of EPDM, the content ratio of ethylene, propylene, and diene, the molecular weight (average molecular weight, molecular weight distribution, etc.), and the molecular structure (linear or branched, etc.), or the degree of cure (degree of crosslinking), etc., are adjusted. Alternatively, the amounts of oil, resin, plasticizer, and stiffener, etc., may be adjusted. For adjusting the degree of cure, the kinds and blending amounts of the additives such as the vulcanizing agent, the crosslinking agent, and vulcanization accelerator are adjusted. It is also possible that two or more kinds of elastomers are used and the blending ratio of these is adjusted.

The thicknesses of the outer layer 8 and the inner layer 9 are not especially limited, however, preferably, the thickness of the outer layer 8 is not less than 0.1 millimeters and not more than 2.0 millimeters, and the thickness of the inner layer 9 is not less than 0.5 millimeters and not more than 5.0 millimeters.

If the thickness of the outer layer 8 is more than 2.0 millimeters or the thickness of the inner layer 9 is less than 0.5 millimeters, there is a possibility that the paper sheet multi-feed preventing member 3 cannot be greatly compressed and deformed in the thickness direction when the paper sheet multi-feed preventing member 3 is brought into contact with the outer peripheral surface 7 of the paper feed roller. Therefore, the effects which improve the separating function and make the paper sheet multi-feed preventing member 3 adaptable to various kinds of paper sheets, make the paper sheet multi-feed preventing member difficult to wear, and make chatter vibration and screeching, etc., hard to occur, cannot be obtained.

On the other hand, if the thickness of the outer layer 8 is less than 0.1 millimeters, the outer layer 8 is easily worn away, and the wear of the outer layer 8 may expose the inner layer 9 in a short time. Further, if the thickness of the inner layer 9 is more than 5.0 millimeters, the inner layer may excessively greatly warp when a load is applied thereto, and a paper feed failure may easily occur.

For preventing the problems described above and forming the paper sheet multi-feed preventing member 3 with more excellent performance, the thickness of the outer layer 8 is preferably not less than 0.2 millimeters and not more than 1.2 millimeters, and especially preferably not less than 0.2 millimeters and not more than 0.5 millimeters within the range. The thickness of the inner layer 9 is preferably not less than 1.0 millimeters and not more than 3.0 millimeters, and especially preferably not less than 2.0 millimeters and not more than 3.0 millimeters within the range.

The outer layer 8 and the inner layer 9 become effective when the outer layer 8 is thin and the inner layer 9 is thick, however, it is not preferable that the outer layer 8 is so thin that it is worn away as described above. Therefore, the thickness ratio (outer layer)/(inner layer) of the outer layer 8 to the inner layer 9 is preferably set so that the ratio of the inner layer 9 is higher than 0.5/0.5, and more preferably 0.5/0.5 to 0.2/0.8.

For forming the paper sheet multi-feed preventing member 3 by laminating any of the outer layers 8 and any of the inner layers 9 described above, an arbitrary adhesive agent, bonding agent, or the like can be used.

It is especially preferable that the paper sheet multi-feed preventing member 3 is formed by laminating the layers 8 and 9 by using a double-sided tape (double-sided sticky tape or double-sided adhesive tape) which has been generally adopted and actually used for fixing the paper sheet multi-feed preventing member 3 to the support base 6, etc., makes the laminating operation easy, and has uniform thickness and does not cause thickness unevenness of the paper sheet multi-feed preventing member 3. As the double-sided tape, double-sided tapes #8800CH and #8810ECO, etc., made by DIC, which have been actually used for industrial purposes, are usable.

For installation in the paper feed mechanism 1, the entire thickness of the paper sheet multi-feed preventing member 3 formed by laminating the layers 8 and 9 is preferably equivalent to that of the conventional single-layer structure. The entire thickness is preferably not less than 1.0 millimeter and not more than 4.0 millimeters, and especially preferably not less than 1.5 millimeters and not more than 3.5 millimeters although it depends on the structure of the paper feed mechanism 1 and the structure of the LBP into which the paper feed mechanism 1 is installed.

By fixing the paper sheet multi-feed preventing member 3 to the support base 6, etc., by using a double-sided tape, etc., in the same manner as conventional in a state in which the outer layer 8 faces upward, the paper sheet multi-feed preventing member can be installed in the paper feed mechanism 1.

EXAMPLES Example 1 Outer Layer

As an outer layer, a non-porous material obtained after blending and kneading a polyester-based thermoplastic elastomer (PELPRENE (registered trademark) P40H made by Toyobo Co., Ltd.) and carbon black (trade name: SEAST SO made by Tokai Carbon, Co., Ltd.) in proportions shown in Table 1, and molding the kneaded material into a sheet shape with a thickness 0.4 millimeters was used.

TABLE 1 Ingredient Parts by mass Polyester-based thermoplastic elastomer 100 Carbon black 1

A measuring sample was prepared by using the same kneaded material, and the type A durometer hardness thereof at a temperature of 23±1° C. and a relative humidity of 55±1% was measured according to the measuring method regulated in JIS K 6353-2006 described above, and the measurement result was A89/S.

A friction coefficient of the outer layer with respect to a plain paper (Proper bond paper (PB PAPER) made by Canon) as a measuring paper was measured by using a surface texture measurement device (TRIBOGEAR (registered trademark) type HEIDON (registered trademark)-14DR made by SHINTO Scientific), and the result was 0.5. As measurement conditions, a temperature was 23±1° C., a relative humidity was 55±1%, a size of the outer layer 8 was 10 millimeters×30 millimeters, the load was 1.96133 N (200 gf), and the speed was 600 mm/min.

Inner Layer

As an inner layer, a non-porous material obtained by blending and kneading butyl rubber (Butyl 268 made by JSR Corporation), carbon black (SEAST SO made by Tokai Carbon Co., Ltd.), paraffin oil (Diana (registered trademark) process oil PW-380 made by Idemitsu Kosan Co., Ltd.), zinc oxide (zinc oxide #2 made by MITSUI MINING & SMELTING Co., Ltd.), stearic acid (trade name: TSUBAKI made by NOF Corporation, powdered sulfur (made by Tsurumi Chemical Industry Co., Ltd.), a thiuram vulcanization accelerator (Nocceler (registered trademark) TET made by Ouchi Shinko Chemical Industrial Co., Ltd.), and a thiazole vulcanization (Nocceler DM made by Ouchi Shinko Chemical Industrial Co., Ltd.) in proportions shown in Table 2, molding the kneaded material into a sheet shape with a thickness of 1.45 millimeters, and vulcanizing the molded material, was used.

A measuring sample was prepared by using the same kneaded material and the type A durometer hardness thereof at a temperature of 23±1° C. and a relative humidity of 55±1% was measured according to the measuring method regulated in JIS K 6253-2006, and the result was A5/S.

Further, a measuring sample was prepared by using the same kneaded material and the rebound resilience thereof at a temperature of 23±1° C. and a relative humidity of 55±1% was measured according to the measuring method regulated in “Testing methods of rebound resilience for rubber, vulcanized or thermoplastic” of JIS K6255-1996, and the result was 2%.

Further, a measuring sample was prepared by using the same kneaded material and the compression set thereof at 70° C.×22 hours according to the measuring method regulated in “Rubber, vulcanized or thermoplastic—Determination of compression set at ambient, elevated or low temperatures” of JIS K 6262-2006, and the result was 10%.

Further, a measuring sample was prepared by using the same kneaded material and the glass transition temperature tg thereof was measured according to the measuring method regulated in “Plastic-determination of dynamic mechanical properties—Part 4: Tensile vibration—Non-resonance method” of JIS K 7244-4, and the result was −15° C. The specific gravity thereof was 1.05.

Paper Sheet Multi-Feed Preventing Member

A paper sheet multi-feed preventing member was formed by laminating the outer layer and the inner layer by using a double-sided adhesive tape (#8800CH with a thickness of 0.15 millimeters, made by DIC, described above). The entire thickness of the paper sheet multi-feed preventing member was 2.0 millimeters.

Example 2

A paper sheet multi-feed preventing member with a thickness of 2.0 millimeters was formed in the same manner as in Example 1 by using, as the inner layer, a non-porous material molded into a sheet shape with a thickness of 1.45 millimeters and vulcanized in the same manner as in Example 1 except that the amount of paraffin oil was set to 10 parts by mass as shown in Table 2.

A measuring sample was prepared by using the kneaded material forming the inner layer and the properties thereof were measured in the same manner as in Example 1, and the type A durometer hardness was A56/S, the rebound resilience was 13%, the compression set was 18%, the glass transition temperature Tg was −20° C., and the specific gravity was 1.2.

Comparative Example 1

A paper sheet multi-feed preventing member with a thickness of 2.0 millimeters was formed in the same manner as in Example 1 by using, as the inner layer, a non-porous material molded into a sheet shape with a thickness of 1.45 millimeters and vulcanized in the same manner as in Example 1 except that the amount of paraffin oil was set to 0 parts by mass, that is, paraffin oil was not blended as shown in FIG. 2.

A measuring sample was prepared by using the kneaded material forming the inner layer and the properties thereof were measured in the same manner as in Example 1, and the type A durometer hardness was A62/S, the rebound resilience was 22%, the compression set was 21%, the glass transition temperature Tg was −20° C., and the specific gravity was 1.34.

TABLE 2 Parts by mass Comparative Ingredient Example 1 Example 2 example 1 Butyl rubber 100 100 100 Carbon black 5 5 5 Paraffin oil 65 10 0 Zinc oxide 5 5 5 Stearic acid 1 1 1 Powdered sulfur 1 1 1 Vulcanization 2 2 2 accelerator TET Vulcanization 1 1 1 accelerator DM

Example 3

As the outer layer, a non-porous material obtained by blending and kneading EPDM (Esprene (registered trademark) E586 made by SUMITOMO CHEMICAL Co., Ltd.), paraffinoil (Diana process oil PW-380 made by Idemitsu Kosan Co., Ltd.), polypropylene (NOVATEC (registered trademark) MG05ES) made by Japan Polypropylene Corporation), styrenic thermoplastic elastomer (SEPTON (registered trademark) HG252 made by Kuraray Co., Ltd.), a crosslinking agent (TACKIROL (registered trademark) 250-III made by Taoka Chemical Co., Ltd.), and carbon black (SEAST SO made by Tokai Carbon Co., Ltd.) in proportions shown in Table 3, molding the kneaded material into a sheet shape with a thickness of 0.4 millimeters, and vulcanizing the molded material, was used.

TABLE 3 Ingredient Parts by mass EPDM 70 Paraffin oil 30 Polypropylene 30 Styrenic thermoplastic elastomer 20 Crosslinking agent 8.4 Carbon black 1

The type A durometer hardness of a measuring sample prepared by using the kneaded material forming the outer layer was measured in the same manner as in Example 1, and the result was A90/S. The friction coefficient was 0.7.

As the inner layer, a non-porous material obtained by blending and kneading NBR (Nipol (registered trademark) 1042 made by ZEON CORPORATION), carbon black (SEAST SO made by Tokai Carbon Co., Ltd.), Di-2-ethylhexyl Sebacate (plasticizer DOS), zinc oxide (Zinc oxide #2 made by MITSUI MINING & SMELTING Co., Ltd.), powdered sulfur (made by Tsurumi Chemical Industry Co., Ltd.), and sulfenamide vulcanization accelerator (Nocceler NS made by Ouchi Shinko Chemical Industrial Co., Ltd.) in proportions shown in Table 4, molding the kneaded material into a sheet shape with a thickness of 1.45 millimeters, and vulcanizing the molded material, was used.

A measuring sample was prepared by using the kneaded material forming the inner layer and the properties thereof were measured in the same manner as in Example 1, and the type A durometer hardness was A32/S, the rebound resilience was 2%, the compression set was 17%, the glass transition temperature Tg was +15° C., and the specific gravity was 1.24.

A paper sheet multi-feed preventing member with a thickness of 2.0 millimeters was formed by laminating the inner layer and the outer layer by using a double-sided adhesive tape in the same manner as in Example 1.

Example 4

A paper sheet multi-feed preventing member with a thickness of 2.0 millimeters was formed in the same manner as in Example 3 by using, as the inner layer, a non-porous material molded into a sheet shape with a thickness of 1.45 millimeters and vulcanized in the same manner as in Example 3 except that the amount of carbon black was set to 25 parts by mass and the plasticizer DOS was not blended as shown in Table 4.

TABLE 4 Parts by mass Ingredient Example 3 Example 4 NBR 100 100 Carbon black 5 25 DOS 15 0 Zinc oxide 3 3 Powdered sulfur 1.5 1.5 Vulcanization 0.7 0.7 accelerator NS

A measuring sample was prepared by using the kneaded material forming the inner layer and the properties thereof were measured in the same manner as in Example 1, and the type A durometer hardness was A57/S, the rebound resilience was 2%, the compression set was 16%, the glass transition temperature Tg was +20° C., and the specific gravity was 1.28.

Conventional Example 1

By molding the same kneaded material containing the ingredients shown in Table 1 as the outer layer of Example 1 into a sheet shape with a thickness of 2.0 millimeters, a non-porous paper sheet multi-feed preventing member having a single-layer structure was formed.

The type A durometer hardness of a measuring sample prepared by using the kneaded material forming the paper sheet multi-feed preventing member was A89/S as described in Example 1. The friction coefficient was 0.5.

Conventional Example 2

By molding the same kneaded material containing the ingredients shown in Table 5 as the outer layer of Example 3 into a sheet shape with a thickness of 2.0 millimeters and vulcanizing it, a non-porous paper sheet multi-feed preventing member having a single-layer structure was formed.

The type A durometer hardness of a measuring sample prepared by using the kneaded material forming the paper sheet multi-feed preventing member was A90/S as described in Example 3. The friction coefficient was 0.7.

Conventional Example 3

A non-porous paper sheet multi-feed preventing member having a thickness of 2.0 millimeters and a single-layer structure was formed in the same manner as in Conventional example 2 except that the amount of paraffin oil was set to 10 parts by mass as shown in Table 5.

The type A durometer hardness of a measuring sample prepared by using the kneaded material forming the paper sheet multi-feed preventing member was measured in the same manner as in Example 1, and the result was A75/S. The friction coefficient was 1.0.

TABLE 5 Parts by mass Conventional Conventional Ingredient example 2 example 3 EPDM 70 70 Paraffin oil 30 10 Polypropylene 30 30 Styrenic thermoplastic elastomer 20 20 Crosslinking agent 8.4 8.4 Carbon black 1 1

Conventional Example 4

A non-porous paper sheet multi-feed preventing member having a single-layer structure was formed by blending and kneading EPDM (Esprene (registered trademark) E586 made by SUMITOMO CHEMICAL Co., Ltd.), polyester-based thermoplastic elastomer (Hytrel (registered trademark) 3046 made by DU PONT-TORAYCO., LTD.), styrenic thermoplastic elastomer (SEPTON HG252 made by Kuraray Co., Ltd.), organic peroxide-based crosslinking agent (Perhexa (registered trademark) 25B made by NOF Corporation), and carbon black (SEAST SO made by Tokai Carbon Co., Ltd) in proportions shown in Table 6, and molding the kneaded material into a sheet shape with a thickness of 2.0 millimeters and vulcanizing it.

TABLE 6 Ingredient Parts by mass EPDM 30 Polyester-based thermoplastic elastomer 70 Styrenic thermoplastic elastomer 15 Organic peroxide-based crosslinking agent 1.1 Carbon black 1

The type A durometer hardness of a measuring sample prepared by using the kneaded material forming the paper sheet multi-feed preventing members was measured in the same manner as in Example 1, and the result was A78/S. The friction coefficient was 0.9.

Evaluation Test

The properties of the paper sheet multi-feed preventing members formed according to Examples and Comparative examples described above were evaluated through the following tests.

Initial Friction Coefficient Measurement

Initial friction coefficients of the surfaces on the outer layer sides of the paper sheet multi-feed preventing members formed according to Examples and Comparative examples described above were measured in the same manner as in measurement of the friction coefficient in the case of only the outer layer described above. That is, the friction coefficient of the outer layer with respect to a plain paper as a measuring paper (Proper bond paper (PB paper) made by Canon) was measured by using a surface texture measurement device (TRIBOGEAR (registered trademark) type HEIDON (registered trademark)-14DR made by SHINTO Scientific). As measurement conditions, the temperature was 23±1° C., the relative humidity was 55±1%, the size of the outer layer 8 was 10 millimeters×30 millimeters, the load was 1.96133 N (=200 gf), and the speed was 600 mm/min. A paper sheet multi-feed preventing member with the initial friction coefficient not less than 0.6 was evaluated as nondefective in friction performance, and a paper sheet multi-feed preventing member with the initial friction coefficient less than 0.6 was evaluated as defective in friction performance.

Wear Resistance Test

After the initial weights of the paper sheet multi-feed preventing members formed according to Examples and Comparative examples described above were measured, the paper sheet multi-feed preventing members were fitted instead of the genuine separation pad of the monochrome LBP (LBP-1420 made by Canon).

Then, after 30000 PPC sheets were made to continuously pass through them in an environment with a temperature of 23±1° C. and a relative humidity of 55±1%, the paper sheet multi-feed preventing members were removed and then their weights after paper passage were measured, and the differences from the initial weights were obtained as wear volumes and the wear resistances were evaluated. That is, the paper sheet multi-feed preventing member with a wear volume not more than 15 mg was evaluated as nondefective in wear resistance, and the paper sheet multi-feed preventing member with a wear volume more than 15 mg was evaluated as defective in wear resistance.

Screeching Evaluation

It was evaluated whether screeching occurred during continuous paper passage of the PPC sheets in the wear resistance test based on the following criteria.

A (very good): Screeching did not occur at all.

B (good): Small screeching occurred, but was determined as no problem in practical use.

C (bad): Screeching frequently occurred.

Multi-Feed

It was evaluated whether multi-feed of two or more PPC sheets occurred during continuous paper passage of the PPC sheets in the wear resistance test based on the following criteria.

B (good): Multi-feed did not occur at all.

C (bad): Multi-feed occurred once or more. The results are shown in Table 7 and Table 8.

TABLE 7 Comparative Example 1 Example 2 example 1 Example 3 Example 4 Inner layer Kind Butyl rubber Butyl rubber Butyl rubber NBR NBR Hardness  A5/S A56/S A62/S A32/S A57/S Outer layer Hardness A89/S A89/S A89/S A90/S A90/S Friction 0.5 0.5 0.5 0.7 0.7 coefficient Properties Initial friction  0.83  0.62  0.55  0.82  0.75 coefficient Wear resistance 6.3 7.3 7.8 4.8 4.9 (mg) Screeching A A A B B Multi-feed B B C B B A: very good B: good C: bad

TABLE 8 Conventional Conventional Conventional Conventional example 1 example 2 example 3 example 4 Single Hardness A89/S A90/S A75/S A78/S layer Friction 0.5 0.7 1.0 0.9 coefficient Properties Initial friction 0.5 0.7 1.0 0.9 coefficient Wear resistance 8.0 6.4 18.4  16.3  (mg) Screeching A C C B Multi-feed C B B B A: very good B: good C: bad

From the results of Conventional examples 1 to 4 in Table 8, it was found that, in the conventional single-layer structures, no matter how much the rubber hardness was adjusted, the wear resistance was insufficient, the initial friction coefficient was small and multi-feed occurred, or the screeching occurred, so that the paper sheet multi-feed preventing member which was excellent in all of these properties could not be obtained with the conventional single layer structures.

From the results of Comparative example 1 in Table 7, it was found that even when the laminate structure including the outer layer and the inner layer which were non-porous was formed, if the type A durometer hardness of the inner layer was more than A60/S, the initial friction coefficient was small and multi-feed occurred.

On the other hand, from the results of Examples 1 and 2, it was found that when the type A durometer hardness of the inner layer was within the range not less than A5/S and not more than A60/S, a paper sheet multi-feed preventing member excellent in all of these properties could be obtained.

From the results of Examples 3 and 4, it was found that even when the kind of the elastomer forming the inner layer was different, if the type A durometer hardness of the elastomer was within the range not less than A5/S and not more than A60/S, a paper sheet multi-feed preventing member excellent in all of the properties could be obtained.

However, comparing Examples 1 and 2 with Examples 3 and 4, it was also confirmed that the effect of suppressing screeching was more excellent in Examples 1 and 2 using butyl rubber having excellent vibrational absorbability as an elastomer forming the inner layer.

Example 5

A paper sheet multi-feed preventing member with a thickness of 2.0 millimeters was formed in the same manner as in Example 1 except that, as the inner layer, a porous material with a thickness 1.45 millimeters was used which was obtained by blending and kneading butyl rubber (Butyl 268 made by JSR Corporation), paraffin oil (Diana process oil PW-380 made by Idemitsu Kosan Co., Ltd.), thermally expandable microcapsule as a foaming agent (Matsumoto Microsphere (registered trademark) F-82 made by Matsumoto Yushi-Seiyaku Co. Ltd.), zinc oxide (zinc oxide #2 made by MITSUI MINING & SMELTING Co., Ltd.), stearic acid (TSUBAKI made by NOF Corporation), powdered sulfur (made by Tsurumi Chemical Industry Co., Ltd.), a thiuram vulcanization accelerator (Nocceler TET made by Ouchi Shinko Chemical Industrial Co., Ltd.), and a thiazole vulcanization accelerator (Nocceler DM made by Ouchi Shinko Chemical Industrial Co., Ltd.) in proportions shown in Table 9, molding the kneaded material into a sheet shape, vulcanizing the molded material, and foaming the foaming agent.

TABLE 9 Ingredient Parts by mass Butyl rubber 100 Paraffin oil 25 Foaming agent 13 Zinc oxide 5 Stearic acid 1 Powdered sulfur 1 Vulcanization accelerator TET 2 Vulcanization accelerator DM 1

A measuring sample was prepared by using the kneaded material forming the inner layer, and the Asker-C hardness thereof at a temperature of 23±1° C. and a relative humidity of 55±1% was measured according to the measuring method regulated in SRIS 0101 described above, and the measurement result was C5.

A measuring sample was prepared by using the kneaded material forming the inner layer and the properties thereof were measured in the same manner as in Example 1, and the rebound resilience was 6%, the compression set was 43%, the glass transition temperature Tg was −20° C., and the specific gravity was 0.15.

Example 6

A paper sheet multi-feed preventing member with a thickness of 2.0 millimeters was formed in the same manner as in Example 1 except that, as the inner layer, a porous material with a thickness 1.45 millimeters was used which was obtained by blending and kneading butyl rubber (Butyl 268 made by JSR Corporation), carbon black (SEAST SO made by Tokai Carbon Co., Ltd.), paraffin oil (Diana process oil PW-380 made by Idemitsu Kosan Co., Ltd.), thermally expandable microcapsule as a foaming agent (Matsumoto Microsphere F-82 made by Matsumoto Yushi-Seiyaku Co. Ltd.), zinc oxide (zinc oxide #2 made by MITSUI MINING & SMELTING Co., Ltd.), stearic acid (TSUBAKI made by NOF Corporation), powdered sulfur (made by Tsurumi Chemical Industry Co., Ltd.), a thiuram vulcanization accelerator (Nocceler TET made by Ouchi Shinko Chemical Industrial Co., Ltd.), and a thiazole vulcanization accelerator (Nocceler DM made by Ouchi Shinko Chemical Industrial Co., Ltd.) in proportions shown in Table 10, molding the kneaded material into a sheet shape, vulcanizing the molded material, and foaming the foaming agent.

The properties of the kneaded material forming the inner layer were measured in the same manner as in Examples 1 and 5, and the Asker-C hardness was C10, the rebound resilience was 8%, the compression set was 48%, the glass transition temperature Tg was −20° C., and the specific gravity was 0.25.

Example 7

A paper sheet multi-feed preventing member with a thickness of 2.0 millimeters was formed in the same manner as in Example 1 except that, as the inner layer, a porous material with a thickness of 1.45 millimeters was used which was obtained by molding into a sheet shape, vulcanizing the molded material, and foaming the foaming agent in the same manner as in Example 6 except that the amount of paraffin oil was set to 15 parts by mass and the amount of foaming agent was set to 5 parts by mass as shown in Table 10.

The properties of the kneaded material forming the inner layer were measured in the same manner as in Examples 1 and 5, and the Asker-C hardness was C25, the rebound resilience was 12%, the compression set was 53%, the glass transition temperature Tg was −20° C., and the specific gravity was 0.32.

Example 8

A paper sheet multi-feed preventing member with a thickness of 2.0 millimeters was formed in the same manner as in Example 1 except that, as the inner layer, a porous material with a thickness of 1. 45 millimeters was used which was obtained by molding into a sheet shape, vulcanizing the molded material, and foaming the foaming agent in the same manner as in Example 6 except that the amount of paraffin oil was set to 10 parts by mass and the amount of foaming agent was set to 3 parts by mass as shown in Table 10.

The properties of the kneaded material forming the inner layer were measured in the same manner as in Examples 1 and 5, and the Asker-C hardness was C40, the rebound resilience was 17%, the compression set was 59%, the glass transition temperature Tg was −20° C., and the specific gravity was 0.58.

Comparative Example 2

A paper sheet multi-feed preventing member with a thickness of 2.0 millimeters was formed in the same manner as in Example 1 except that, as the inner layer, a porous material with a thickness of 1.45 millimeters was used which was obtained by molding into a sheet shape, vulcanizing the molded material, and foaming the foaming agent in the same manner as in Example 6 except that the amount of foaming agent was set to 1 part by mass and the paraffin oil was not blended as shown in Table 10.

The properties of the kneaded material forming the inner layer were measured in the same manner as in Examples 1 and 5, and the Asker-C hardness was C60, the rebound resilience was 25%, the compression set was 70%, the glass transition temperature Tg was −20° C., and the specific gravity was 0.75.

TABLE 10 Parts by mass Comparative Ingredient Example 6 Example 7 Example 8 example 2 Butyl rubber 100 100 100 100 Carbon black 5 5 5 5 Paraffin oil 20 15 10 0 Foaming agent 10 5 3 1 Zinc oxide 5 5 5 5 Stearic acid 1 1 1 1 Powdered sulfur 1 1 1 1 Vulcanization 2 2 2 2 accelerator TET Vulcanization 1 1 1 1 accelerator DM

Example 9

A paper sheet multi-feed preventing member with a thickness of 2.0 millimeters was formed in the same manner as in Example 7 except that a non-porous material obtained by molding the same kneaded material as that of Conventional example 3, containing the ingredients of Table 5, into a sheet shape with a thickness of 0.4 millimeters, was used as the outer layer.

The type A durometer hardness of the kneaded material forming the outer layer was A75/S as described in Conventional example 3. The friction coefficient was 1.0.

Example 10

A paper sheet multi-feed preventing member with a thickness of 2.0 millimeters was formed in the same manner as in Example 3 except that, as the inner layer, a porous material with a thickness 1.45 millimeters was used which was obtained by blending and kneading NBR (Nipol 1042 made by ZEON CORPORATION), carbon black (SEAST SO made by Tokai Carbon Co., Ltd.), Di-2-ethylhexyl Sebacate (plasticizer DOS), thermally expandable microcapsule as a foaming agent (Matsumoto Microsphere F-82 made by Matsumoto Yushi-Seiyaku Co. Ltd.), zinc oxide (Zinc oxide #2 made by MITSUI MINING & SMELTING Co., Ltd.), powdered sulfur (made by Tsurumi Chemical Industry Co., Ltd.), and a sulfenamide vulcanization accelerator (Nocceler NS made by Ouchi Shinko Chemical Industrial Co., Ltd.) in proportions shown in Table 11, molding the kneaded material into a sheet shape, vulcanizing the molded material, and foaming the foaming agent.

TABLE 11 Ingredient Parts by mass NBR 100 Carbon black 5 DOS 15 Foaming agent 3 Zinc oxide 3 Powdered sulfur 1.5 Vulcanization accelerator NS 0.7

The properties of the kneaded material forming the inner layer were measured in the same manner as in Examples 1 and 5, and the Asker-C hardness was C25, the rebound resilience was 10%, the compression set was 62%, the glass transition temperature Tg was +18° C., and the specific gravity was 0.3.

Example 11

A paper sheet multi-feed preventing member with a thickness of 2.0 millimeters was formed in the same manner as in Example 10 except that a non-porous material obtained by molding the same kneaded material as that of Conventional example 4, containing the ingredients of Table 6, into a sheet shape with a thickness of 0.4 millimeters, was used as the outer layer.

The type A durometer hardness of the kneaded material forming the outer layer was A78/S as described in Conventional example 4. The friction coefficient was 0.9.

Example 12

A paper sheet multi-feed preventing member with a thickness of 2.0 millimeters was formed in the same manner as in Example 10 except that a non-porous material obtained by molding the same kneaded material as that of Conventional example 3, containing the ingredients of Table 5, into a sheet shape with a thickness of 0.4 millimeters, was used as the outer layer.

The type A durometer hardness of the kneaded material forming the outer layer was A75/S as described in Conventional example 3. The friction coefficient was 1.0.

Comparative Example 3

A paper sheet multi-feed preventing member with a thickness of 2.0 millimeters was formed in the same manner as in Example 1 except that, as the inner layer, a porous material with a thickness 1.45 millimeters was used which was obtained by blending and kneading NBR (Nipol 1042 made by ZEON CORPORATION), carbon black (SEAST SO made by Tokai Carbon Co., Ltd.), thermally expandable microcapsule as a foaming agent (Matsumoto Microsphere F-82 made by Matsumoto Yushi-Seiyaku Co. Ltd.), zinc oxide (Zinc oxide #2 made by MITSUI MINING & SMELTING Co., Ltd.), powdered sulfur (made by Tsurumi Chemical Industry Co., Ltd.), and a sulfenamide vulcanization accelerator (Nocceler NS made by Ouchi Shinko Chemical Industrial Co., Ltd.) in proportions shown in Table 12, molding the kneaded material into a sheet shape, vulcanizing the molded material, and foaming the foaming agent.

TABLE 12 Ingredient Parts by mass NBR 100 Carbon black 25 Foaming agent 1 Zinc oxide 3 Powdered sulfur 1.5 Vulcanization accelerator NS 0.7

The properties of the kneaded material forming the inner layer were measured in the same manner as in Examples 1 and 5, and the Asker-C hardness was C62, the rebound resilience was 18%, the compression set was 22%, the glass transition temperature Tg was +18° C., and the specific gravity was 0.75.

The properties of the paper sheet multi-feed preventing members formed in Examples and Comparative examples were evaluated through the tests described above. The results are shown in Table 13 and Table 14.

TABLE 13 Comparative Example 5 Example 6 Example 7 Example 8 example 2 Inner layer Kind Butyl rubber Butyl rubber Butyl rubber Butyl rubber Butyl rubber Hardness C5 C10 C25 C40 C60 Outer layer Hardness A89/S A89/S A89/S A89/S A89/S Friction 0.5 0.5 0.5 0.5 0.5 coefficient Properties Initial friction 0.9  0.87 0.8  0.73  0.58 coefficient Wear resistance 6.0 6.2 6.5 7.1 7.9 (mg) Screeching A A A A A Multi-feed B B B B C A: very good B: good C: bad

TABLE 14 Comparative Example 9 Example 10 Example 11 Example 12 example 3 Inner layer Kind Butyl rubber NBR NBR NBR NBR Hardness C25 C25 C25 C25 C62 Outer layer Hardness A75/S A90/S A78/S A75/S A89/S Friction 1.0 0.7 0.9 1.0 0.5 coefficient Properties Initial friction 1.3  0.94 1.2 1.3  0.58 coefficient Wear resistance 14.7  4.6 12.8  14.8  7.5 (mg) Screeching A B A B A Multi-feed B B B B C A: very good B: good C: bad

From the results of Comparative example 2 in Table 13, it was found that even when the laminate structure including the non-porous outer layer and the porous inner layer was formed, if the Asker-C hardness of the inner layer was more than C50, the initial friction coefficient was small and multi-feed occurred.

On the other hand, from the results of Examples 5 to 8, it was found that when the Asker-C hardness of the inner layer was within the range not less than C5 and not more than C50, a paper sheet multi-feed preventing member excellent in all of the properties could be obtained.

From the results of Examples 9 to 12 and Comparative example 3 in Table 14, it was found that even when the kinds of the elastomers forming the inner layer and the outer layer were different, if the Asker-C hardness of the inner layer was within the range not less than C5 and not more than C50, a paper sheet multi-feed preventing member excellent in all of the properties could be obtained.

However, comparing Examples 5 to 8 with Examples 10 to 12, it was also confirmed that the effect of suppressing screeching was more excellent in Examples 5 to 8 using butyl rubber having excellent vibrational absorbability as an elastomer forming the inner layer. 

1. A paper sheet multi-feed preventing member being planar and including an outer layer which comes into contact with a paper sheet and an inner layer laminated on the outer layer, wherein the inner layer has a type A durometer hardness not less than A5/S and not more than A60/S, and the outer layer has a rubber hardness higher than that of the inner layer.
 2. The paper sheet multi-feed preventing member according to claim 1, wherein the inner layer is made of a non-porous material of butyl rubber.
 3. The paper sheet multi-feed preventing member according to claim 2, wherein the thickness of the outer layer is not less than 0.1 millimeters and not more than 2.0 millimeters, and the thickness of the inner layer is not less than 0.5 millimeters and not more than 5.0 millimeters.
 4. The paper sheet multi-feed preventing member according to claim 1, wherein the thickness of the outer layer is not less than 0.1 millimeters and not more than 2.0 millimeters, and the thickness of the inner layer is not less than 0.5 millimeters and not more than 5.0 millimeters.
 5. A sheet multi-feed preventing member being planar and including an outer layer which comes into contact with a paper sheet and an inner layer laminated on the outer layer, wherein the inner layer has an Asker (registered trademark)-C type hardness not less than C5 and not more than C50, and the outer layer has a rubber hardness higher than that of the inner layer.
 6. The paper sheet multi-feed preventing member according to claim 5, wherein the inner layer is made of a porous material of butyl rubber.
 7. The paper sheet multi-feed preventing member according to claim 6, wherein the thickness of the outer layer is not less than 0.1 millimeters and not more than 2.0 millimeters, and the thickness of the inner layer is not less than 0.5 millimeters and not more than 5.0 millimeters.
 8. The paper sheet multi-feed preventing member according to claim 5, wherein the thickness of the outer layer is not less than 0.1 millimeters and not more than 2.0 millimeters, and the thickness of the inner layer is not less than 0.5 millimeters and not more than 5.0 millimeters. 